The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Emissions test systems collect exhaust gas produced by an engine and measure the concentrations of emissions in the exhaust gas. The concentration of an emission measured during a period is multiplied by the mass flow rate of exhaust gas during that period to obtain the mass flow rate of the emission. The mass flow rate of the emission is then multiplied by the duration of the period to obtain the total mass of the emission in the exhaust gas produced by the engine during the period.
A constant volume sampling (CVS) system is a type of emissions test system that enables determining the mass of emissions in exhaust gas without measuring the flow rate of the exhaust gas, which simplifies emission mass determinations. A CVS system typically includes a dilution tunnel in which exhaust gas and a dilution gas are mixed, a sample probe that directs a portion of the diluted exhaust gas from the dilution tunnel to a sample collector, and a blower disposed downstream of the dilution tunnel. The blower draws a constant volume of diluted exhaust gas through the dilution tunnel. Thus, the exhaust gas flow rate may be determined by subtracting the flow rate of the dilution gas from the flow rate of the diluted exhaust gas.